Update PKG-Copyright

* doc/pkg-copyright.txt: Update and extend.

This should now cover all included packages. The GnuPG parts
have been updated with the text from pkg-copyright.txt in
GnuPG.

This should now include every package we include as a binary.

For better readability i grouped some packages with the same
license together. The licenses will be installed by kcoreaddons.

The overall GPLv3 license is already installed by GnuPG and
for GnuPG VS-Desktop in license.rtf.

• GnuPG-Bug-Id: T6834